1. Field of the Invention
The present invention relates to a position detecting device for detecting a motor pole position and a synchronous motor driving device using the position detecting device. More particularly, the present invention relates to a position detecting device and a synchronous motor driving device using the same, which are suitably used to perform acceleration and deceleration over the range from a zero speed (stopped state) to a high rotation speed.
2. Description of the Related Art
As one of devices for driving a synchronous motor (hereinafter referred to simply as a “motor”), there is known a type of driving the motor by using a position detecting device which detects a rotor pole position. Here, the term “position detecting device” means a device, such as a resolver or an absolute rotary encoder, which can not only detect a motor rotational angle during rotation, but also determine an absolute position in the stopped state. In order to achieve driving of the motor with high efficiency, however, it is essential to detect the phase of a counter electromotive voltage (i.e., the pole position of a motor rotor) by the position detecting device with high accuracy. Several techniques adapted for that purpose are also known.
For example, Patent Document 1 (Japanese Patent No. 3315847) discloses a technique of employing a detection unit for executing position calculation using a linear zone of a sensor signal, and correcting sensitivity and an offset based on maximum and minimum values of the sensor signal.
Also, Patent Document 2 (Japanese Patent No. 3397013) discloses a technique of employing a deviation detecting unit which detects a voltage and a current supplied to an armature coil to estimate a rotor pole position, and which detects a position deviation from an error between the estimated rotor pole position and a detected rotor rotational position, and correcting the detected position deviation.